This application is an application under 35 U.S.C. Section 371 of International Application Number PCT/FR99/01428 filed on Jun. 15, 1999.
The present invention relates to water-repellent aqueous emulsions, in particular for dampproofing buildings and building materials such as stone, concrete, mortar, terracotta (bricks, tiles, etc.) and wood, as well as to a process for preparing the emulsion and to a dampproofing process.
Moisture is the cause of damage in buildings: cracks caused by frost, appearance of molds and lichens, loss of heat insulation, etc. For this reason, compositions intended for dampproofing building materials have been developed.
Water-repellent agents in aqueous phase are more difficult to prepare. The difficulties are especially in giving them an efficacy which is close to those in solvent phase and also sufficient stability over time.
Patent application WO 97/47569 proposes, for dampproofing materials such as wood, cellulosic materials, masonry and concrete, an aqueous emulsion comprising:
(1) at least one resin, comprising at least one unit T or Q, of average formula (I)
MaDbTcQd(O1/2R)e
xe2x80x83in which:
M=R1R2R3SiO1/2, D=R4R5SiO2/2, T=R6SiO3/2 and Q=SiO4/2;
R1, R2, R3, R4, R5 and R6 are alkyl radicals and R is a hydrogen atom or an alkyl radical;
the symbols a, b, c and d represent the ratio of the silicon atoms of type M, D, T and Q, respectively, relative to the total number of silicon atoms in the resin of average formula (I), and
the symbol e represents the number of groups xe2x89xa1Si(O1/2R) relative to the total number of silicon atoms in the resin of average formula (I);
xe2x80x83and (2) the product of reaction between:
(a) at least one polyfunctional aromatic or aliphatic amine containing from 2 to 25 carbon atoms;
(b) at least one carboxylic acid or anhydride containing from 3 to 22 atoms;
(c) at least one crosslinking agent which is a water-soluble metal.
Now, the Applicant has developed novel compositions based on silicone resin and on the components (2a) and (2b) specified above, and also containing at least one nonionic, anionic and/or amphoteric surfactant. These novel compositions have water-repellent power that is at least equivalent to those of the prior art, or even water-repellent power that is superior to those of the prior art, depending on the materials applied.
One of the main objects of the invention is to develop aqueous emulsions that are more stable when applied on materials, which means that the silicone resin in the droplets of the emulsion is not released immediately on contact with the material, and thus no phenomenon of repulsion of the material with respect to the successive layers of the said emulsion applied is observed. In this respect, higher stability is particularly observed on application to materials whose surface is alkaline (e.g.: mortar, cement mortar).
Another object of the invention is to propose aqueous emulsions of improved applicability, i.e. reinforced wettability, which is reflected by a more homogeneous distribution.
Another object of the invention is to propose aqueous emulsions which have an increased speed of imbibition (or coefficient of capillarity), i.e. the active principles contained in the droplets of the emulsion penetrate more quickly and easily into the materials applied.